The present invention relates to a network I/O system and a network configuring method in which signals at digital I/O ports corresponding to a multipoint for digitally controlling a plurality of controlled devices are multiplexed to reduce the number of wirings in an industrial machinery etc.
The network I/O system provides a host computer, a central communication unit connected with the host computer, and a plurality of terminal communication units each having digital I/O ports. The central communication unit and the plurality of terminal communication units configure a network configuration by using a multi-drop connection, a daisy-chain connection, etc.
In the past, the input/output of data between the host computer and the plurality of controlled devices such as sensors, actuators, etc. which are disposed dispersedly, has performed by connecting the controlled devices directly to the host computer, therefore, a number of wirings are required.
The network I/O system configures a network in which the host computer is connected with the plurality of dispersedly disposed controlled devices, and the signals at digital I/O ports are multiplexed to realize the data input/output between the host computer and the plurality of controlled devices by a simple connection of using a small number of wirings. This has been used mainly in the industrial field in which a number of the controlled devices are easily dispersed in such as industrial machineries for manufacturing automobiles, machine tools, chip mounters, etc.
Here, it is required to set an identification number, in the terminal communication unit, for designating a sending destination and a sending source of a communication so that the communication is performed between the host computer and the terminal communication units each connected with the controlled device.
In the past, a setting of the identification number in the terminal communication units has been performed by the following method. That is, a switch and ROM (Read-only Memory) are provided on the respective terminal communication units and non-overlapped values are assigned respectively to the terminal communication units by using the switch and ROM in manual when incorporating the network I/O system in a machine.
Here, when changing or adding a network configuration, the system must be built up correctly by not only resetting the identification number for each of the above-mentioned terminal communication units but also figuring out accurately, by a system user, a type of the controlled device connected with the respective terminal communication units and the network configuration as well as the identification number set in the terminal communication units. In the past, the following procedure has been performed in manual: confirmation of the network configuration configured by the respective terminal communication units and the type of controlled device connected with the terminal communication units; and confirmation of the identification number set in the respective terminal communication units.
For a purpose of solving the above-mentioned problem, JP-A-2005-260828 has been known as a technique for setting a MAC (Media Access Control) address as a unique address in advance when manufacturing the terminal communication unit and dynamically setting an IP (Internet Protocol) address for every communication card slot. However, in the case of the above-mentioned method, it is required to have a large load such that an address management must be maintained from when manufacturing the terminal communication unit to when transferring it to the user. Further, when a major scale configuration widely used with the MAC address etc. cannot be used, a large number of man-hour is required for setting a new unique address and for manufacturing the terminal communication unit.